Begin with a forced restart of your iPad:
Force restart iPad (models with Face ID or with Touch ID in the top button)
If your iPad doesn’t have the Home button, do the following:
- Press and quickly release the volume button nearest to the top button.
- Press and quickly release the volume button farthest from the top button.
- Press and hold the top button.
- When the Apple logo appears, release the top button.
Force restart iPad (models with the Home button)
Press and hold the top button and the Home button at the same time. When the Apple logo appears, release both buttons.
If you have forgotten the ScreenTime passcode, the procedures outlined within this link should resolve the problem:
If you forgot your Screen Time passcode - Apple Support
If your iPad is capable of supporting iPadOS 13.x or later, you should update to the most current version before attempting to resolve a forgotten ScreenTime passcode. Recent iPadOS updates have introduced a mechanism whereby a forgotten ScreenTime passcode can be reset without wiping the iPad.
To reset a forgotten ScreenTime passcode on older versions of iOS/iPadOS, the iPad must be complete reset “as new”, losing all locally stored data:
Settings > General > Reset > Erase All Content & Settings
In this situation, you’ll not be able to restore your data from an iCloud or iTunes backup - as the forgotten passcode is integral to the backup.